WON’T PLAY BALL: Yankees catcher Francisco Cervelli, working in the bullpen yesterday in Tampa, would not go into detail about his link to Biogenesis, a Miami anti-aging clinic. Photo: N.Y. Post: Charles Wenzelberg

HERE’S THE PITCH: Mariano Rivera works off the mound, throwing 25 pitches, during his first camp workout. (Charles Wenzelberg/New York Post)

TAMPA — He wore No. 42, and appeared lean and regal, and his mere presence in late morning on the back diamonds of Yankee spring training initiated calls of “Mariano, Mariano” from fans stationed behind the fences that encase George M. Steinbrenner Field.

Yet the first day of work for pitchers and catchers still elicited this question:

Is that Mariano Rivera?

On first glance, it sure looked like Rivera. But there was something different in his gait as he went through a 25-pitch bullpen session and fielding drills.

It was not overt — no dragging leg or dramatic limp — and you might not have noticed without intense scrutiny. But, of course, we are in the intense scrutiny portion of Rivera’s program since he blew out his ACL last May 3 and is the lone player in any major league camp born in the 1960s.

We intensely scrutinize because unique athleticism is in the very forefront of how Rivera climbed from poor fisherman’s son in Panama to Greatest Closer Ever. In the genus of closers, he always has been more balletic swan than fire-breathing Goose. His movements graceful, flowing, precise. That allowed him to repeat his delivery and, thus, pinpoint pitches like few men ever while retaining a quick-twitch genius on and around the mound.

So you look for deviation that could undermine gifts that have elevated Rivera to a grand master in the art of throwing a baseball. And there is the slightest favoring of the surgically repaired knee, a tiny hiccup away from the seamless athleticism seared into your retina from hundreds and hundreds of viewings.

Maybe it is nothing, maybe it will not affect a single pitch in 2013 or perhaps it is just part of a post-surgical process back to same as he ever was and this is only the first day of camp. For Rivera might just be acclimating to a lightweight knee brace that he acknowledged he was wearing and probably will continue to wear during the season. It could still just be about the recovery clock. Rivera put himself at a nine on a scale of 1 to 10, but vowed, “I won’t be a nine [when camp breaks]. I will be at a 10 when I am finished.”

Who would bet against him? He is Mariano Rivera, seemingly as super natural as superstar. Consider that Yankees strength and conditioning head Dana Cavalea worked at the Stadium during the winter with the closer and said even post-injury and now 43 that Rivera remained an age-defying athletic marvel. “He’s The Man,” Cavalea proclaimed. “He’s a freak.”

Joe Girardi, a true believer and optimist to the 10th power, said, “I don’t think Mo will be any different than if he didn’t have the knee injury.”

And J.R. Murphy, a minor leaguer who yesterday caught Rivera for the first time, said, “It looked like on television: easy, effortless and a lot of strikes.”

The Yankees need this. Need Rivera. Need him to be his brilliant self so they can check a concern off a bigger list than any time in recent memory. Rivera might have coyly thrown a verbal cutter to the media, veering the theme yesterday from the present to the future with his revelation that he knows if he is going to retire or not after this season, but keeping that a secret for now.

The Yankees don’t mind the guessing game for 2014, but not now. They hardly need to add in-season closer audition among David Aardsma, Joba Chamberlain and David Robertson to their to-do list.

Rivera actually sounded and acted like a man planning to make 2012 his final season at this time last year. But he announced nothing, suffered the knee injury shagging flies in Kansas City and pledged he would not end his career in that fashion — carried off a field.

So an uber-dedicated player with nothing left to prove put his mind and body back into the grind because it turns out five rings, the all-time saves record and title of Greatest Closer Ever was not enough. He yearns to win more games, chase another championship, be who he always has been. After the knee surgery. As the last playing vestige of the 1960s.

We have wondered about when the end will come for Rivera often as he has aged. And he never deviated. Now he faces his greatest challenge, and you don’t bet against him because he is Mariano Rivera.

But you scrutinize the guy in the No. 42 jersey more than ever because, well, you want to make sure it is still Mariano Rivera.